1. Field of the Invention
The present invention relates to an optical switch circuit network for controlling paths for the propagation of optical signals.
2. Description of the Background Art
It has been customary to implement a number of input ports and output ports, i.e., a large-scale architecture with optical switches by sequentially combining the optical switches. Various schemes heretofore proposed for combining optical switches include an optical path cross-connect system taught in T. Nishi, et al. xe2x80x9cOptical Switch Architectures for Optical Path Cross-Connectxe2x80x9d, Proceedings of the 1998 General Conference of the Institute of Electronics, Information and Communication Engineers of Japan, B-10-97, March 1998. The cross-connect system constitutes an optical switch circuit network with optical matrix switches arranged in three consecutive stages. This, however, brings about a substantial loss in the optical matrix switches. Effective architectures for increasing the number of input ports and output ports with two stages of optical matrix switches have not been reported yet.
An optical switch circuit network using thermo-optical (TO) switches is disclosed in A. Watanabe, etal. xe2x80x9c8xc3x9716 delivery and coupling switch board for 320 Gbit/s throughput optical path cross-connect systemxe2x80x9d, Electronics Letters, Vol. 33, No. 1, pp. 67-68, Jan. 2, 1997. The TO switches each include means for switching an optical path by varying the resistance of an optical waveguide with heat. Each TO switch is located at the intersection of one input and one output. The network drives only one of the TO switches connected to a desired input and a desired output for the purpose of saving drive power.
However, the problem with the above TO switch scheme is that it has to serially connect TO switches equal in number to the inputs or the outputs and therefore results in a prohibitive total length. Specifically, when the TO switch scheme is used to construct an Nxc3x97N optical switch circuit network, it is necessary to switch Nlog2N TO switches at the input port side and switch Nlog2N TO switches at the output port side. In the worst case, therefore, the network has to switch 2Nlog2N TO switches in total.
It is therefore an object of the present invention to provide an optical switch circuit network needing only two stages of optical matrix switches.
It is another object of the present invention to provide an optical switch circuit network capable of scaling down the individual optical matrix switch.
It is a further object of the present invention to provide an optical switch circuit network which is short despite the use of TO switches and capable of reducing power necessary for driving TO switches while stabilizing the power.
In accordance with the present invention, an optical switch circuit network including nr (n and r being positive integers) input ports and nr output ports includes r input optical switches arranged at the input side and each having n of the nr input ports, m (m being a positive integer) 1xc3x97r optical switches and an nxc3x97m optical switch for selectively connecting the n input ports and m 1xc3x97r optical switches, and r output optical switches arranged at the output side and each having n of the nr output ports, m rxc3x971 optical switches and an mxc3x97n optical switch for selectively connecting said n output ports and m rxc3x971 optical switches. The i-th (i being an integer between 1 and m) 1xc3x97r optical switch of each of the input optical switches is connected to the i-th rxc3x971 optical switch of each of the output optical switches.
Also, in accordance with the present invention, an optical switch circuit network including nr input ports and nr output ports includes r/h (h being a positive integer) input optical switches arranged at the input side and having nh of the nr input ports, m hxc3x97r optical switches and h nxc3x97m optical switches each being connected to a particular one of n of the nr input ports to thereby switch a path between the n input ports and said m hxc3x97r optical switches, and r/h optical output switches arranged at the output side and having nh of the nr output ports, m rxc3x97h optical switches and h mxc3x97n optical switches each being connected to particular one of n of the nr output ports to thereby switch a path between the n output ports and the m rxc3x97h optical switches. The i-th (i being an integer between 1 and m) hxc3x97r optical switch of each of the input optical switches is connected to the i-th rxc3x97h optical switch of each of the output optical switches by a tape-like optical fiber constituted by h connect lines.
Further, an optical switch circuit network including nr input ports and nr output ports of the present invention includes r/h input optical switches arranged at the input side and having nh of the nr input ports, m/hxe2x80x2 (hxe2x80x2 being a positive integer) nhxc3x97hxe2x80x2r optical switches and nh/hxe2x80x2 hxe2x80x2xc3x97m/hxe2x80x2 optical switches each being connected to particular one of hxe2x80x2 of the nr input ports to thereby switch a path between the hxe2x80x2 input ports and m/hxe2x80x2 nhxc3x97hxe2x80x2r optical switches, and r/h output optical switches arranged at the output side and having nh of the nr output ports, m/hxe2x80x2 hxe2x80x2rxc3x97nh optical switches and nh/hxe2x80x2 m/hxe2x80x2xc3x97hxe2x80x2 optical switches each being connected to particular one of hxe2x80x2 of the nr output ports to thereby switch a path between the hxe2x80x2 output ports and hxe2x80x2rxc3x97nh optical switches. The hxe2x80x2xc3x97m/hxe2x80x2 optical switches each are connected to said nhxc3x97hxe2x80x2 optical switches by tape-like optical fibers each comprising hxe2x80x2 connect lines. The m/hxe2x80x2 optical switches each are connected to the r/nh optical switches by tape-like optical fibers each having hxe2x80x2 connect lines. The input optical switches are connected to the output optical switches by tape-like optical fibers each having h connect lines.
Moreover, in accordance with the present invention, an optical switch circuit network including N input ports and N output ports includes 2n input sections each having N/2n of the N input ports, 2n N/2nxc3x97N/2n input optical switches, and 1xc3x972 optical switches arranged in an n-stage tree configuration and connecting the input ports and input optical switches, and 2n output sections each having N/2n of the N output ports, 2n N/2nxc3x97N/2n output optical switches, and 1xc3x972 optical switches arranged in an n-stage tree configuration and connecting the output ports and output optical switches. The j-th (j being an integer between 1 and 2n) input optical switch of the i-th (i being an integer of 2n or smaller) input section is connected to the i-th output optical switch of the j-th output section.